The present invention relates to an LED indicator device for an AC power plug or socket and, more particularly, to an LED indicator device for indicating on/off and/or incorrect power connection or short circuit of an AC power plug or socket such as a fixed AC power socket, a socket of an AC adaptor, or a plug or socket of an AC extension cord.
AC power sockets include fixed AC power sockets, sockets of AC extension cords, and sockets of AC adapters. Fixed AC power sockets are electrically connected to an external AC power source. An AC extension cord includes a plug for coupling with an AC power socket in a building. The AC extension cord further includes a socket casing having one or more sockets for coupling with a plug of an electric appliance to supply external AC power through the plug and the socket of the AC extension cord to the electric appliance.
However, users are often not aware of the existence and on/off state of the fixed AC power socket or the AC extension cord. To solve this problem, a small neon lamp is provided on the socket casing. Particularly, the neon lamp is lit to show the extension cord and to indicate that the power is on. However, the life of the neon lamp is only about 30,000 hours. Furthermore, when it is desired to detect electrical connection of the hot wire, neutral wire, and grounding wire of AC power lines, only simple tests for identifying these wires can be done. It is impossible to identify correct electrical connection or short circuit of an AC power plug or socket.
A need exists for a device for indicating electrical connection between wires and/or on/off state of an AC power plug or socket